1. Field of the Invention
The present invention relates to chromium carbide-cemented carbide compositions, articles made therefrom and their processing.
2. Background
A chromium carbide (Cr3C2) nickel based (i.e., greater than 50 w/o Cr3C2) grade of cemented carbide has been made for many years. However, it has been difficult to control the grain growth of chromium carbide during liquid phase sintering. The chromium carbide grain size of this material is coarse. These coarse grains result in a material having reduced strength, toughness, hardness/abrasion resistance which greatly limits its commercial application. An example of a prior art commercial grade of chromium carbidexe2x80x94nickel is a composition reportedly having 85 w/o chromium carbide 15 w/o nickel, Rockwell A hardness of 88.5, density of 7.00 g/cc, transverse rupture strength of 100 ksi (689 N/mm2) and A04 porosity. A microstructure of this prior art material is shown in FIG. 1.
It would, therefore, be desirable to produce a chromium carbide based (i.e., at least 50 w/o Cr3C2) cemented carbide composition having a combination of high corrosion resistance with high strength, toughness and hardness/abrasion resistance.
In accordance with the present invention, an article of manufacture is provided having a chromium carbide based composition having a combination of excellent corrosion resistance and good wear resistance, strength and toughness.
In accordance with the present invention, the chromium carbide based composition has chromium carbide grains, having an average grain size of less than 10 xcexcm disbursed in and cemented together by a nickel and/or chromium based binder.
Preferably, the average grain size of the chromium carbide grains are less than 8 xcexcm and more preferably less than 5 xcexcm.
Preferably, the chromium carbide based composition has a porosity rating of A02 or better.
Preferably, the chromium carbide composition has an average transverse rupture strength of at least 875 N/mm2, more preferably at least 1000 N/mm2, and most preferably at least 1075 N/mm2.
A particularly preferred composition in accordance with the present invention has a nickel content of 13 to 17 weight percent and a chromium carbide content of 83 to 87 weight percent, with a chromium carbide average grain size of less than 8 xcexcm, a porosity rating of A02 or better, a Rockwell A hardness of at least 89.5, and an average transverse rupture strength of at least 1075 N/mm2.
These and other aspects of the invention will become more apparent upon consideration of the drawings, which are briefly described below, in conjunction with the Detailed Description of the Invention.